Hmm, I think people are being a bit unfair. It's worthy of a C, perhaps a B since I think the use of language is good.
However, I'll give you a few more tips if you want them. I'm aiming for an A* too.
You have to expand this a little. A lot of repetition is being used, and the only real point you're emphasising is that Crooks is a victim of racism. Which is true, though to secure an A* grade you need to reach out to a wider theme:
''Crooks illustrates social prejudice. He is intelligent, reads books, and like any other human being needs warmth and companionship. He is denied these, not through any fault of his own but rawly through the fact that he's black. Yet if there is a theme of racial prejudice here it is almost a sub division of a wider theme, that of
loneliness. ''
''Like Candy, Crooks is an example of Steinbeck's
compassion and a further illustration of the way in which loneliness can corrupt and destroy a man. His cynicism about the world is summed up when he says, ''Nobody gets to heaven, and nobody gets no land''.
Also, ''He is partly disabled in a society which values human beings simply on their ability to provide a service'' is a valid point.
I would also like to address your point regarding Curley's wife: I have altered it a bit!
''The true horror of Crooks's situation is revealed when he dares to challenge a white woman married to a white man. Curley's wife has done little to warrant respect, though she may have your sympathy. This girl, by virtue of her race rather than her attributions as a human being can crush Crooks in little more than a sentence: ''You know what I can do to you if you open your trap?'' I hope that's okay.
Also, bring up the theme of Dreams and reality. This is so important.
You have to talk about how Crooks realises the dream is nothing more than a dream (regarding the George and Lennie's dream of owning a farm):
''Crooks realises that the dream is nothing more than a dream; doomed to failure because the real world does not allow dreams to come to fruition. Like Crooks, we want to believe in the dream despite everything we know, and like Crooks we come to realise that it is a dream is very much impossible.'' Or something along those lines?
Basically, a more sophisticated use of language is needed to achieve 90% though it's very do-able. Identify key themes throughout the novel, and relate to them through your answer and you'll be in a good position for the exam.
Good luck and I hope this helped!!